Combination magnetic particle clutch and brake assembly

ABSTRACT

A combination magnetic particle clutch and brake device and a method of assembling the same which comprises a single output shaft having a pair of spaced discs mounted thereon, with one disc used as part of a brake unit and the other disc used as part of a clutch unit. Brake and clutch driver coils are provided for energizing each of the units. Bearing assemblies are provided at opposite ends of the device to rotatably support the output shaft and an input rotor pole which is part of the clutch unit. The device is designed so as to facilitate assembly and to maintain very close tolerances in spacing of the parts without need for shimming.

United States Patent Hendershot, Jr. et al.

1 May 23, 1972 [54] COMBINATION MAGNETIC PARTICLE CLUTCH AND BRAKEASSEMBLY [72] Inventors: James R. Hendershot, Jr.; Robert F.

Searle, Amherst, both of NH.

[73] Assignee: Vibrac Corporation, Chelmsford, Mass.

[22] Filed: July 9, 1970 21 Appl. No.5 53,651

Feiertag 1 92/21 .5

2,573,065 10/1951 Salenne ..192/21.5

Primary Examiner-Benjamin W. Wyche Assistant Examiner-Randall HealdAttorney-Schiller & Pandiscio [57] ABSTRACT A combination magneticparticle clutch and brake device and a method of assembling the samewhich comprises a single output shaft having a pair of spaced discsmounted thereon, with one disc used as part of a brake unit and theother disc used as part of a clutch unit. Brake and clutch driver coilsare provided for energizing each of the units. Bearing assemblies areprovided at opposite ends of the device to rotatably support the outputshaft and an input rotor pole which is part of the clutch unit. Thedevice is designed so as to facilitate assembly and to maintain veryclose tolerances in spacing of the parts without need for shimming.

l 1 Claims, 1 Drawing Figure PATENTEDmza I972 3.664.473

James R Hendersho/fl Robert F Sear/e INVENTORS.

A TTOR/VEKS.

COMBINATION MAGNETIC PARTICLE CLUTCH AND BRAKE ASSEMBLY This inventionrelates to magnetic torque transmitting devices and more particularly tothose devices employing magnetic particles in a combined clutch andbrake assembly.

Magnetic particle devices of various types are well known to the art.Most commonly they are constructed to function as quick-actingelectrically actuated clutches or brakes. Combination magneticallyenergized clutch and brake devices are also known in the art and areextremely useful in providing quick-response, selectively energizablecombination clutch and brake units which may be employed, for example,in a tape driven mechanism. The present invention is concerned with animprovement that greatly simplifies the construction and assembly aswell as the accuracy and reliability of such combination magneticparticle clutch and brake assemblies. Typically prior devices of thetype to which the invention relates consist of a single rotatablymounted output shaft having two or more radially extending discs mountedfixedly thereon. The brake assembly consists of first and secondstationary members mounted about one of the discs with a spacingtherebetween which is filled with magnetic particles, plus a coil toselectively establish a magnetic flux between the stationary members andthe disc in order to magnetically lock the particles and preventrelative rotation between the disc and the stationary magnetic members.The clutch assembly comprises a rotor structure mounted about but spacedfrom another of the discs, with-the intervening spaces being filled withmagnetic particles. The clutch assembly is provided with a coil toselectively establish a magnetic flux between the rotor structure andthe associated disc in order to lock the particles intotorque-transmitting chains coupling the disc and rotor structure. Therotor serves as an input or driving member to impart rotation to theoutput shaft when the clutch coil is energized. Bearing assemblies areprovided at the ends and intermediate the ends of the unit forpermitting rotation of the rotor structure and the output shaft. Thesebearing units are subjected to both axial and radial thrust. Such priordevices have been difficult to fabricate and assemble and problems havebeen incurred in eliminating end play between the relatively moveableparts. Accordingly, it has been necessary to employ shims in order tomaintain the necessary close tolerance spacing between the discs andtheir respective armatures and also to properly maintain the othercomponents in optimum operating relation to each other.

Accordingly, an object of the present invention is to provide acombination magnetic particle clutch and brake assembly which isrelatively simple to construct and assemble.

Another object of this invention is to provide a combination magneticparticle clutch and brake assembly which is constructed so as to provideand maintain very close tolerances for the gaps on each side of eachdisc.

Still another object of the present invention is to provide acombination magnetic particle clutch and brake assembly which in itsconstruction and assembly eliminates the necessity for shimming theseveral parts.

A further important object is to provide a magnetic particle clutch orbrake assembly that is designed so that the magnetic particles can beloaded under dynamic conditions to achieve a predetermined torque,whereby to facilitate production of a number of devices with identicalperformance characteristics.

Another object of the present invention is to provide an improved methodof making magnetic particle clutch and brake assemblies.

Still another object of the present invention is to provide acombination magnetic particle clutch and brake assembly in which theoutput shaft extends only partially through the assembly and the rotorstructure has plugging means for preventing the escape of magneticparticles from the gap around the clutch unit.

The above objects,features and advantages of the apparatus of thepresent invention, as well as others, are accomplished by providing acombination magnetic particle clutch and brake assembly comprising anoutput shaft having first and second spaced discs affixed thereto. Thebrake unit includes a stationary magnetic armature member disposed onopposite sides of the first disc and spaced therefrom so that magneticparticles may be loaded into the space. A brake driver coil is providedwhich when energized establishes a flux path through the armature memberand the first disc. The clutch unit includes a rotor member enclosingand spaced from the second disc so that magnetic particles may be loadedinto the space. A clutch driver coil is provided which when energizedestablishes a magnetic flux path through the rotor member, the statormember and the second disc. Sealing means prevent escape of magneticparticles from the spaces. The device is designed so that portions ofthe clutch and brake sections form discrete subassemblies and the outputshaft and rotor member are rotatably supported by means which eliminatethe necessity for shimming any of the parts of the assembly.

Other objects and many of the attendant advantages of this invention arebelieved to be apparent from the following specification which is to beconsidered together with the accompanying drawing, wherein:

The FIGURE is a longitudinal partial sectional view of a combinationmagnetic particle clutch and brake assembly constituting a preferredembodiment of the present invention.

Turning now to the figure, there is illustrated a combination magneticparticle clutch and brake assembly 10 comprising stationary field coils,an input unit, an output unit, and bearing assemblies mounted in acylindrical housing 12 fitted at one end with an annular base or shaftsupport 14. Housing 12 and shaft support 14 are made of magneticmaterial and may be press fitted as shown, snap-fitted or screwed to oneanother (not shown) at a portion indicated by numeral 16. Shaft support14 serves as a member of the magnetic stator, or armature of a brakeunit which will be described later.

The inner end of shaft support 14 is reduced in diameter as shown at 18and is secured to a second annular armature member 20 by means of aspacer sleeve 22. Member 20 is made of magnetic material and sleeve 22is made of non-magnetic material, preferably stainless steel. Sleeve 22may be secured to shaft support 14 and member 20 .by a press fit or byother means such as by welding or by pins or screws (not shown). lnnertransversely extending faces 24 and 26 of shaft support 14 and member 20respectively are spaced from one another by sleeve 22 to define a gap 28and function as poles of the brake armature to develop a magnetic fieldthrough portions of the brake unit.

A pair of annular field coils 30 and 32 each wound around bobbins 34 and36 respectively and of known construction are secured in grooves inhousing 12. Both bobbins 34 and 36 abut opposing faces of an interveningring 38 projecting from the wall of housing 12. Bobbin 34 is held inabutting position with one face of ring 38 by a face 40 of base 14. Ring38 also functions as a stator pole. The opposite ends of coils 30 and 32are each connected to pairs of leads 42 and 44 respectively whichproject out of housing 12 through suitable openings 46 and 48respectively. Leads 42 and 44 are used to couple coils 30 and 32 to anexternal power source (not shown) whereby they may be energized.

An input unit identified generally by numeral 49 is provided andcomprises a hollow input rotor 50 which partially extends outsidehousing 12. The portion of rotor 50 which extends outside housing 12 hasa keyway 53 formed on the outer surface thereof which allows the rotor50 to be coupled to a source of torque input. Attached to the inner endof rotor 50 by a spacer sleeve 54 is a member 52 constructed like member20. Sleeve 54 may be secured to rotor 50 and member 52 by a press fit orby other suitable means such as screws (not shown). Rotor 50 and member52 are made of magnetic material so as to function as armature membersof the clutch unit, while sleeve 54 is made of a non-magnetic material.Rotor 50 and member 52 have inner transversely extending faces 56 and 58respectively which are spaced from one another to define a gap 60 andfunction as poles to direct a magnetic field through portions of theclutch unit. Mounted within housing 12 adjacent to but spaced from rotor50 is an annular member 62 which is made of magnetic material andfunctions as a stator pole. (It is to be noted that housing 12 functionsas the stator of the clutch and is also part of the magnetic circuit ofthe brake unit.) One side of member 62 engages and holds bobbin 36against the adjacent side surface of the inwardly extending ring 38 ofthe wall housing 12.

Rotor 50 is rotatably supported in housing 12 by means of a bearingassembly comprising a pair of bearings 66 and 68 separated by a bearingspacer 70. The exact positions of bearings 66 and 68 are determined atone end by an annular retainer ring 72, which snaps into a groove formedin the inner wall of housing 12, and a shoulder 73 on rotor 50 againstwhich bearing 66 abuts. Bearing 68 is held in firm position by aretainer ring 72, which snaps into a groove formed on the outer surfaceof rotor 50, and by a staked portion 76 on the end of housing 12. It isto be noted that staking as at 76 is for convenience and that the sameresult could be achieved by means of a snap ring or by a threaded nutscrewed onto and locked to housing 12. Bearings 66 and 68 and spacer 70are all held firmly in position by retainer ring 72 and shoulder 73 atone end and retainer ring 74 and staked portion 76 at the other endwithout necessity for shimming any of the parts. Retainer ring 72 alsoengages annular member 62 whereby the latter bears against bobbin 36 tohole it in proper position against one face of ring 38. It is essentialthat the retainer ring 74 be made so that when inserted in the groove inrotor 50 in will provide sufficient axial force to appropriatelypre-load bearings 66 and 68. Preferably it is formed with across-sectional bow. However, is also could be wavy like a wavy springwasher or wedge shaped in cross-section so as to take up all play andeliminate the need for shims.

The base 14 has an axial bore or opening 80 defined by an inner wall 82.Inner wall 82 functions as a bearing support for an output unitidentified generally by numeral 84. The output unit 84 comprises a shaft86 constructed of non-magnetic material and a pair of discs 88 and 90.The shaft 86 is rotatably supported by means of a bearing assemblycomprising a pair of bearings 92 and 94 abutting one another and a thirdbearing 96 separated from bearings 92 and 94 by a bearing spacer 98. Itis to be noted that the number of bearings used may vary depending uponwhat is required to support the external load applied to shaft 84. Theouter race of bearing 96 engages a retainer ring 100 which snaps into agroove formed in the wall 82, while its inner race engages a shoulder101 on shaft 86. The inner race of bearing 92 is held in firm positionby a retainer ring 102 which snaps into a groove formed on the outersurface of shaft 86, while its inner race is held against axial movementby a staked portion 104 on the end of base 14. The staking at 104 couldbe omitted and the same result achieved by means of a retaining ringmounted in base 14 or a nut screwed onto and locked to the end of bore14. Retainer ring 102 is of the same type as ring 74 and could bereplaced by some other means such as a nut if the end of shaft 86 werethreaded. Bearings 92, 94 and 96 and bearing spacer 98 are all firmlyheld in position between retainer ring 100 and shoulder 101 at one endand retainer ring 102 and staked portion 104 at the other end withoutnecessity for shimming any of the parts.

Disc 88 is secured to shaft 86 so that it is positioned to extendradially between faces 24 and 26 in gap 28. Disc 88 may consist of asingle member made of magnetic material. Preferably, however, itconsists of two concentric rings of different thicknesses, with theinner ring 1 being non-magnetic and comprising a radially-extendingflange formed integral with shaft 86. lf it is not formed integrallywith shaft 86, ring 110 may be press-fitted welded, brazed orinductively soldered onto shaft 86. Outer ring 112, which has athickness or dimension in the direction parallel to the axis of shaft 86less than the thickness in the same direction of inner ring orprojection 110, is made of a magnetic material such as No. 2 relaysteel. The outer diameter of the outer ring 112 is slightly less thanthe inner diameter of sleeve 22 so as to provide a gap therebetween. Theouter ring 112 may be attached to the inner ring or projection 1 10 ofshaft 86 in a variety ways, as for example, by press fitting orinductive soldering.

Mounted in sealing engagement with the opposite faces of inner ring andalso the shaft 84 are face seals 114 and 116. Seals 114 and 116 aresecured to and housed in circular seal cups 118 and 120 respectivelywhich have a generally L- shaped cross-section so as to provideprojecting edges 112 and 124 respectively that surround and engage theouter ends of seals 114 and 116 respectively. The cups 118 and 120 aremade of non-magnetic material such as brass and the seals 114 and 1 16housed therein are made of a suitable resilient sealing material such asrubber or plastic-impregnated felt. The outer surfaces 126 and 128 ofedges 122 and 124 respectively are press fitted against the inner wall82 of base 14 and member 20 respectively. The inner diameter of cups 118and 120 is greater than the adjacent diameter of the shaft 84, and theedges 122 and 124 extend axially of shaft 86 to just short of engagementwith magnetic ring 112. The ends of face seals 114 and 116 adjacent theprojecting edges 122 and 124 of cups 118 and 120 together with saidedges and the faces 24 and 26 adjacent the outer ring 112 and sleeve 22function to close off the annular space defining gap 28 between disc 88and the base 14 and member 20. This space of gap is ,filled with drymagnetic particles 130. Disc 88 serves as part of a brake unit whosefunctioning will be described in conjunction with the operation of theassembly 10.

The disc 90 also may be a single disc of magnetic material. Preferably,however, it consists of two concentric rings of different thicknesses.Inner ring is made of non-magnetic material. Outer ring 142 is made of amagnetic material such as No. 2 relay steel. The outer diameter of theouter ring 142 is slightly less than the inner diameter of sleeve 54 soas to provide a gap therebetween. The outer ring 142 may be attached tothe inner ring 140 in a variety of ways, as for example, by pressfitting or inductive soldering. Disc 90 has a D-shaped opening (notshown) and is mounted on the end of shaft 86 on a portion 144 which iscorrespondingly keyed in the form of a D. The disc 90 is held in placeon keyed D portion 144 of the shaft 86 by a washer 146 and a cap screw148 having a cap 149. Engaging the inner ring 140 is a face seal 150.Seal 150 is secured to and housed in a circular non-magnetic seal cup152 which has a generally L-shaped cross-section so as to provideprojecting edge 154 that surrounds and engages the outer end of seal150. The cup 152 is made of non-magnetic material and does not engageshaft 84. The seal 150 housed therein is made of a suitable resilientsealing material such as rubber or plastic-impregnated felt. The outersurface 156 of edge 154 is press fitted against the inside surface ofmember 52. The outer diameter of cup 152 is greater than the outerdiameter of the inner ring 140, and the edge 154 extends axially ofshaft 42 to just short of engagement with magnetic ring 142. The end offace seal 150 adjacent the projecting edge 154 of cup 152 together withsaid edges and the faces 56 and 58 of rotor 50 and member 52respectively adjacent the outer ring 142 and sleeve 54 function to closeoff the annular space of gap 60 between disc 90 and the rotor 50 andmember 52. This space is filled with dry magnetic particles 158. Disc 90serves as part of a clutch unit whose functioning will be described inconjunction with the operation of the assembly 10.

Face seals 114, 116 and 150 are annular members which are ofsubstantially rectangular cross-section when viewed in section as in thefigure. When mounted in the assembly 10, their side surfaces engage theside faces of inner rings 110 and 140 respectively tightly enough toform a firm seal therewith and yet permit rotation of shaft 86 and discs88 and 90. Additionally, with respect to their inner diameters, theseals are sized so that when they are seated, they are radiallycompressed and make firm engagement with shaft 86. These seals serve toprevent the escape of the magnetic particles from gaps 28 and 60,thereby increasing the life of the assembly.

A plug 160 is provided in the center opening in rotor 50.. Plug 160 hasan end face 162 with a beveled edge 164 for ease of insertion of theplug which is positioned immediately adjacent and very slightly spacedfrom washer 146. Plug 160 serves to prevent magnetic particles 158 fromescaping from gap 60 through the opening passing through rotor 50. Plug160 has a pressure relief hole 166 passing therethrough which afterinserted into position within rotor 50 is sealed by a rivet 168. Othersealing means such as epoxy potting compound could be used to seal hole166 when plug 160 is properly seated. At an end 170 of hole 166, aportion of plug 160 is relieved to permit the entry of cap 149 of screw148 which permits the plug to be spaced as close as is necessary towasher 146. Instead of hole 166, the necessary pressure relief could beprovided by scoring plug 160 on its outer periphery to provide airpassages from gap 60. In such case, after plug 160 is inserted, the airpassages would be sealed, for example, with an epoxy potting compound.

A clutch-brake device as above described lends itself to combining partsthereof in at least two discrete subassemblies and allows the magneticparticles 138 and 158 to be loaded into their respective gaps underdynamic conditions so that the quantity of particles can be adjusted toprovide exactly the torque desired. The base 14 is provided with one ormore threaded holes such as shown at 114 for mounting the base on arigid support to facilitate assembly and also to mount the fullyassembled device to a machine or system in which it is to be used.Assembly of the device is described below.

One subassembly operation commences with insertion of retainer ring 100into its groove in the inner wall 82 of base 14, with the latter mountedon a suitable fixed support (not shown) by means of a cap screw screwedinto hole 180. Next bearing 96, spacer 98, and bearings 94 and 92 areconsecutively inserted into opening 80 from the left end of base 14.When they are fully inserted and properly positioned with opening 80 inbase 14, the end of base 14 is staked as shown at 104 to lock thisbearing assembly in place. Cup 118 containing face seal 114 is theninserted from the right end of base 14 in opening 80 so that cup 118abuts retainer ring 100. Cup 118 is press fitted into position. Thenshaft 86 with disc 88 already thereon is inserted thereon the right endof base 114 into opening 80 so as to pass through bearings 96, 94 and 92and project outside the left end of base 14. Shaft 86 is then locked inplace by application of retainer ring 102. Next sleeve 22 is securedonto the right end 18 of base 14, followed by the attachment of armaturemember 20. The sleeve 22 is dimensioned so as to accurately provide thecorrect spacing required between faces 24 and 26.

The next subassembly operation consists of insertion of bobbin 34carrying brake coil into housing 12 and then securing the housing ontobase 14 so as to captivate bobbin 34 as shown. The housing 12 may besecured to base 14 by a press-fit or by means of screws (not shown)screwed into the base through the side wall of the housing. Then shaft84 is coupled to a motor through a torque transducer, preferably of thetype shown in U. S. Pat. No. 3,495,452, and the leads of coil 30 arecoupled to a suitable power supply. Next the power supply is turned onand some magnetic powder is poured into the gap 28. The magnetic fieldestablished by coil 30 pulls the magnetic particles together in the gap28. Then while the coil is still energized the motor is turned on torotate shaft 84. The magnetized particles magnetically couple disc 88 tothe pole faces 24 and 26 with the result that a torque resistance toshaft rotation is established. The torque transducer provides ameasurement of the torque resistance. Assuming that initially the torqueresistance is too low, additional powder is poured into the gap untilthe torque resistance is at the desired level. Then the said motor isturned off and the cup 120 containing face seal 116 is press-fitted intoplace. Coil 30 may be turned off before or after face seal 1 16 isinstalled.

The next subassembly operation consists of insertion of bobbin 36carrying coil 32, stator pole member 62 and retaining ring 72 intohousing 12.

Another subassembly consists of assembling clutch rotor 50, sleeve 54,annular pole member 52 and disc 90. Sleeve 54 is press-fitted onto theleft end of rotor 50, followed by insertion of disc 90 into gap 60 andattachment of member 52. Sleeve 54 is dimensioned so as to accuratelyprovide the correct spacing between faces 56 and 58. Then cup 150carrying face seal 150 is press-fitted in position through the left-handend of pole member 52.

Next the clutch rotor assembly is installed in housing 12. This may bedone from the left-hand end of the housing by first detaching thehousing from base 14. Preferably, however, it is done from the righthand end of the housing in the manner now to be described. The clutchrotor assembly is inserted from the right hand end of the housing withseal cup 152 fitting over shaft 84. Shaft 84 is then rotated until itsright hand end portion 144 is keyed with disc 90, after which washer 146is applied and secured in place by cap screw 148. Then bearing 66,spacer 70 and bearing 68 are inserted in the order named from the righthand end of housing 12 which is then staked as shown at 76. The rotorassembly is pulled axially to the right to bring its shoulder tightagainst the inner race of bearing 66 and secured against leftward axialmovement by application of retainer ring 74 as shown.

Next magnetic particles are loaded into gap 60 from the right hand endof rotor 50 through the opening therein. The amount of magneticparticles required to give the desired clutching torque between rotor 50and shaft 84 is determined by energizing clutch coil 32 and drivingshaft 84 through a motor and torque transducer in the manner describedabove in connection with loading particles into the gap 28 of the brakeunit. After the desired amount of magnetic powder has been loaded intogap 60, plug 160 is press-fitted into place as shown. Hole 166 in plug160 allows escape of air displaced by the plug as it is inserted andthereby prevents a pressure buildup which might force the particles outof the gap. Once plug 160 is in place, hole 166 is closed off byinsertion of rivet 168 therein.

The device 10 may be assembled as above described without need forshimming of the several parts while accurately'maintaining the spacingof the component parts with one another and close tolerances of the gapsin which the discs 88 and 90 are located. Thus, it is possible toachieve very close tolerances such that gaps of 0.015 inches may bemaintained on each side of each of the discs without the necessity forshimming parts. Because of the close tolerances that may be maintainedbetween parts and because the torque characteristics of the brake andclutch units may both be adjusted by varying the amount of powder in thegaps as above described, it is possible to produce a number ofbrake-clutch devices with substantially identical performancecharacteristics. 7

Operation of the above-described combination clutch and brake assembly10 will now be explained. When coil 32 is energized via leads 44, amagnetic field is established across the particles 158 through thestator pole 62, rotor 50, the outer ring 142 of disc 90, member 52 andring 38 of housing 12. With such flux linkage across the particles 158,the latter will lock in chains between rotor 50, member 52 and outerring 142, thereby coupling the input unit 49 with the output unit 84.The transmitted torque is controllable by varying the strength of themagnetic field. Rotation of rotor 50, member 52, and disc 90 togetherwith shaft 86 serves as a clutch unit which may be operated at anydesired torque level or between any two or more torque levels byselection of appropriate energizing currents.

Once the clutch unit is operating as described above, if his desired tobrake the rotation of shaft 86 of output unit 84, coil 32 is deenergizedwhile coil 30 via leads 42 is simultaneously energized. Withenergization of coil 30 a magnetic field is established across theparticles in gap 28 through ring 38 of housing 12, base 14, member 20and the outer ring 112 of disc 88. The flux linkage across particles 30will cause them to lock in chains between base 14, member 20 and ring112 of disc 88, whereby shaft 86 is braked. The clutch and brake unitsboth have very fast response, making the device suitable for fastresponse applications as, for example, magnetic tape drive units.

It is to be understood that the invention is not limited in itsapplication to the details of construction and arrangement of partsspecifically shown or described and that within the scope of theappended claims, it may be practiced otherwise than as spacificallyshown or described.

We claim:

1. A combination magnetic particle clutch and brake device comprising:

a hollow housing made of a magnetic material;

an output shaft having first and second radially extending discs spacedapart therealong and rotatable therewith;

a brake unit including a hollow magnetic armature and a brake drivercoil to establish a magnetic flux path through said hollow armature andsaid first disc when energized;

said hollow armature being disposed within and secured to said housingat one end thereof and said brake driver coil being disposed within andsecured to said housing in surrounding relation to said hollow armature;

said hollow armature having poles disposed on opposite sides of saidfirst disc in axial spaced relation thereto, and means extending betweensaid poles closing off the space between said poles and said disc, thespace between said first disc and said poles being filled with magneticparticles;

a clutch unit disposed within said housing, said clutch unit comprisinga hollow magnetic rotor having poles disposed on opposite sides of saidsecond disc in coaxial spaced relation thereto and means extendingbetween said poles closing off the space between said poles and saidsecond disc, the space between said second disc and said rotor beingfilled with magnetic particles and one end of said hollow rotorprotruding from the other end of said housing so as to serve as an inputshaft for said device;

said output shaft extending through said hollow armature with one endthereof protruding from one end of said device and the other end thereofterminating within said rotor;

a clutch driver coil to establish a magnetic flux path through saidrotor and said second disc when energized, said clutch driver coil beingdisposed within and secured to said housing in surrounding relation tosaid rotor;

sealing means to prevent said magnetic particles from escaping from saidspaces; and

bearing means rotatably supporting said shaft and said rotor, saidbearing means consisting of a first bearing assembly at one end of saiddevice rotatably mounting said output shaft to said hollow armature; anda second bearing assembly at the opposite end of said device rotatablymounting said rotor to said housing.

2. An assembly as set forth in claim 1 wherein said output shaft extendsthrough said hollow armature with one end thereof protruding from oneend of said device and the other end thereof terminating within saidrotor and further wherein said second disc is on said other end of saidshaft and said sealing means includes radially extending sealing membersdisposed on opposite sides of said first disc for preventing escape ofparticles from said space between said first disc and said armaturemember;

a radially extending sealing member disposed on one side of said seconddisc; and

a plug disposed in and secured to said rotor immediately adjacent to andslightly spaced from the other side of said second disc.

3. A device according to claim 2 wherein said plug is adapted to provideat least one pressure relief opening which allows air to escape from thespace around said second disc without escape of magnetic particles whensaid plug is inserted in said rotor opening.

4. A device according to claim 1 wherein said second disc is located atsaid other end of said output shaft.

5. A device according to claim 4 wherein said first bearing assembly islocated between said one end of said output shaft and said first discand said second bearing assembly is located between said other end ofsaid output shaft and the outer end of said rotor.

6. A device according to claim 5 wherein said shaft has a shoulderbetween said one end thereof and said first disc; and further whereinsaid first bearing assembly comprises a first retaining ring concentricwith but spaced from said shaft mounted in said hollow armature on theside of said first disc opposite that of said second disc,

a first bearing abutting said first retaining ring and said shoulder,

a spacer abutting said first bearing;

a second bearing abutting said spacer; and

means on said output shaft and said hollow armature holding saidbearings and said spacer in said abutting relation and cooperating withsaid retaining ring and said shoulder to prevent axial movement of saidoutput shaft relative to said hollow armature member.

7. A device according to claim 6 wherein said last mentioned meansincludes a second retaining ring mounted in a groove in said outputshaft.

8. a device according to claim 5 wherein said rotor has a shoulder onthe side of said second disc opposite that of said first disc; and saidsecond bearing assembly comprises a retaining ring concentric with butspaced from said rotor mounted inside of and secured to said housing onthe side of said second disc opposite that of said first disc;

a first bearing disposed so that one end abuts said retaining ring andsaid shoulder;

a spacer abutting said first bearing;

a second bearing abutting said spacer; and

means on said housing and said rotor holding said first and secondbearings and said spacer in said abutting relation and cooperating toprevent axial movement of said rotor relative to said housing.

9. A combination magnetic particle clutch and brake device comprising;

a hollow housing and a base secured in one end of said housing;

said base including a pair of axially spaced poles of magnetic materialand means connected to said poles and extending across the space betweensaid poles so as to form a first chamber, said base also having an axialbore; a shaft rotatably mounted in said axial bore; a first disc on saidshaft extending into said first chamber; magnetic particles in saidfirst chamber and sealing means preventing escape of said particles fromsaid first chamber; v

a hollow rotor including a pair of axially spaced poles of magneticmaterial and means connected to said poles and extending across thespace between said poles to form a second chamber, said hollow rotorbeing rotatably mounted in said housing in axial alignment with saidshaft;

a second disc on said shaft extending into said second chamber;

magnetic particles in said second chamber and sealing means in saidrotor preventing escape of magnetic particles from said second chamber;and

first and second selectively energizeable coils in said housing, saidfirst coil being positioned so that when energized it produces magneticflux through the poles of said base, said first disc and the magneticparticles in said first chamber, said second coil being positioned sothat when energized it produces magnetic flux through said rotor poles,said second disc and the magnetic particles in said second chamber;

one end of said shaft extending out of said base and one end of saidrotor extending out of said housing, said second disc being releasablysecured to the other end of said shaft by releasable means accessiblethrough said one end of said rotor.

10. A method of adjusting the torque characteristic of a magneticparticle coupling device of the type comprising a rotatable shaft with amagnetic disc thereon, a hollow magnetic armature surrounding said shaftand having (a) poles disposed on opposite sides of said disc in axialspaced relation thereto and (b) a non-magnetic sleeve connected to andextending between said poles in radial spaced relation to said disc forclosing off the space between said poles and said disc so as to form achamber of magnetic particles, means rotatably supporting said shaft insaid armature, an electrically energizable coil for establishing amagnetic field through said armature and said disc, and first and secondsealing members disposed between said shaft and said armature onopposite sides of said disc, said method comprising introducing magneticpowder to said chamber while only said first sealing member is in place,said powder being introduced to said chamber from the side opposite saidfirst sealing member, energizing said coil to compact the powder in saidchamber, measuring the torque required to rotate said shaft in saidarmature while said coil is energized, varying the amount of powder insaid chamber until the torque required to rotate said shaft in saidarmature with said coil energized reaches a predetermined level, andthen installing said second sealing member.

11. A device according to claim 4 wherein said second disc is formed asa separate member, and further including means accessible through saidhollow rotor for releasably afiixing said second disc to said outputshaft.

1. A combination magnetic particle clutch and brake device comprising: ahollow housing made of a magnetic material; an output shaft having firstand second radially extending discs spaced apart therealong androtatable therewith; a brake unit including a hollow magnetic armatureand a brake driver coil to establish a magnetic flux path through saidhollow armature and said first disc when energized; said hollow armaturebeing disposed within and secured to said housing at one end thereof andsaid brake driver coil being disposed witHin and secured to said housingin surrounding relation to said hollow armature; said hollow armaturehaving poles disposed on opposite sides of said first disc in axialspaced relation thereto, and means extending between said poles closingoff the space between said poles and said disc, the space between saidfirst disc and said poles being filled with magnetic particles; a clutchunit disposed within said housing, said clutch unit comprising a hollowmagnetic rotor having poles disposed on opposite sides of said seconddisc in coaxial spaced relation thereto and means extending between saidpoles closing off the space between said poles and said second disc, thespace between said second disc and said rotor being filled with magneticparticles and one end of said hollow rotor protruding from the other endof said housing so as to serve as an input shaft for said device; saidoutput shaft extending through said hollow armature with one end thereofprotruding from one end of said device and the other end thereofterminating within said rotor; a clutch driver coil to establish amagnetic flux path through said rotor and said second disc whenenergized, said clutch driver coil being disposed within and secured tosaid housing in surrounding relation to said rotor; sealing means toprevent said magnetic particles from escaping from said spaces; andbearing means rotatably supporting said shaft and said rotor, saidbearing means consisting of a first bearing assembly at one end of saiddevice rotatably mounting said output shaft to said hollow armature; anda second bearing assembly at the opposite end of said device rotatablymounting said rotor to said housing.
 2. An assembly as set forth inclaim 1 wherein said output shaft extends through said hollow armaturewith one end thereof protruding from one end of said device and theother end thereof terminating within said rotor and further wherein saidsecond disc is on said other end of said shaft and said sealing meansincludes radially extending sealing members disposed on opposite sidesof said first disc for preventing escape of particles from said spacebetween said first disc and said armature member; a radially extendingsealing member disposed on one side of said second disc; and a plugdisposed in and secured to said rotor immediately adjacent to andslightly spaced from the other side of said second disc.
 3. A deviceaccording to claim 2 wherein said plug is adapted to provide at leastone pressure relief opening which allows air to escape from the spacearound said second disc without escape of magnetic particles when saidplug is inserted in said rotor opening.
 4. A device according to claim 1wherein said second disc is located at said other end of said outputshaft.
 5. A device according to claim 4 wherein said first bearingassembly is located between said one end of said output shaft and saidfirst disc and said second bearing assembly is located between saidother end of said output shaft and the outer end of said rotor.
 6. Adevice according to claim 5 wherein said shaft has a shoulder betweensaid one end thereof and said first disc; and further wherein said firstbearing assembly comprises a first retaining ring concentric with butspaced from said shaft mounted in said hollow armature on the side ofsaid first disc opposite that of said second disc, a first bearingabutting said first retaining ring and said shoulder, a spacer abuttingsaid first bearing; a second bearing abutting said spacer; and means onsaid output shaft and said hollow armature holding said bearings andsaid spacer in said abutting relation and cooperating with saidretaining ring and said shoulder to prevent axial movement of saidoutput shaft relative to said hollow armature member.
 7. A deviceaccording to claim 6 wherein said last mentioned means includes a secondretaining ring mounted in a groove in said output shaft.
 8. a devIceaccording to claim 5 wherein said rotor has a shoulder on the side ofsaid second disc opposite that of said first disc; and said secondbearing assembly comprises a retaining ring concentric with but spacedfrom said rotor mounted inside of and secured to said housing on theside of said second disc opposite that of said first disc; a firstbearing disposed so that one end abuts said retaining ring and saidshoulder; a spacer abutting said first bearing; a second bearingabutting said spacer; and means on said housing and said rotor holdingsaid first and second bearings and said spacer in said abutting relationand cooperating to prevent axial movement of said rotor relative to saidhousing.
 9. A combination magnetic particle clutch and brake devicecomprising; a hollow housing and a base secured in one end of saidhousing; said base including a pair of axially spaced poles of magneticmaterial and means connected to said poles and extending across thespace between said poles so as to form a first chamber, said base alsohaving an axial bore; a shaft rotatably mounted in said axial bore; afirst disc on said shaft extending into said first chamber; magneticparticles in said first chamber and sealing means preventing escape ofsaid particles from said first chamber; a hollow rotor including a pairof axially spaced poles of magnetic material and means connected to saidpoles and extending across the space between said poles to form a secondchamber, said hollow rotor being rotatably mounted in said housing inaxial alignment with said shaft; a second disc on said shaft extendinginto said second chamber; magnetic particles in said second chamber andsealing means in said rotor preventing escape of magnetic particles fromsaid second chamber; and first and second selectively energizeable coilsin said housing, said first coil being positioned so that when energizedit produces magnetic flux through the poles of said base, said firstdisc and the magnetic particles in said first chamber, said second coilbeing positioned so that when energized it produces magnetic fluxthrough said rotor poles, said second disc and the magnetic particles insaid second chamber; one end of said shaft extending out of said baseand one end of said rotor extending out of said housing, said seconddisc being releasably secured to the other end of said shaft byreleasable means accessible through said one end of said rotor.
 10. Amethod of adjusting the torque characteristic of a magnetic particlecoupling device of the type comprising a rotatable shaft with a magneticdisc thereon, a hollow magnetic armature surrounding said shaft andhaving (a) poles disposed on opposite sides of said disc in axial spacedrelation thereto and (b) a non-magnetic sleeve connected to andextending between said poles in radial spaced relation to said disc forclosing off the space between said poles and said disc so as to form achamber of magnetic particles, means rotatably supporting said shaft insaid armature, an electrically energizable coil for establishing amagnetic field through said armature and said disc, and first and secondsealing members disposed between said shaft and said armature onopposite sides of said disc, said method comprising introducing magneticpowder to said chamber while only said first sealing member is in place,said powder being introduced to said chamber from the side opposite saidfirst sealing member, energizing said coil to compact the powder in saidchamber, measuring the torque required to rotate said shaft in saidarmature while said coil is energized, varying the amount of powder insaid chamber until the torque required to rotate said shaft in saidarmature with said coil energized reaches a predetermined level, andthen installing said second sealing member.
 11. A device according toclaim 4 wherein said second disc is formed as a separate member, andfurther including means acCessible through said hollow rotor forreleasably affixing said second disc to said output shaft.